While we are on naughty things to do with phones… There were a couple of techniques with the old coin phones. One that required a bit of skill was dialing the number you wanted by flashing the switch hook. That required some skill, and the techs in the exchange could often hear that it was being done, and would drop the call for you. Another was to put the money in as per normal, but instead of pushing the button when the called party picked up, you just talked very loudly into the earpiece. This worked well enough as a microphone to let you talk to the other person. Then when you had finished, you pushed button B to get your money back. I tried this as a lad to prove that it worked, but never made serious use of it.
Later when I was working for the NZ Post office, there was a trunk between most of the PABX's around the district. They weren't all that well documented, but of course idle fingers tried all sorts of likely numbers just to see where they went. To find out, you would dial a likely code and then 0 for the operator. When she (which it generally was back then) answered you would ask where she was. This tended to confuse them a bit, but in this way we managed to document quite a lot of the system. Once we had a good idea of the setup, we could dial a call into and out of lots of the local PABX's, then back to another phone on our one. That would ring OK, but having been through so many PABX's. the voice was often too weak to hear. (PABX…private automatic branch exchange, like the ones larger businesses have.)
The in the eighties the office I was working in was equipped with one of the new PABX's with all sorts of fancy features. Like "ring me back when the guy I want to call hangs up" and "Ring me back when he is there". So one lunchtime, I had a lot of fun after everyone else had gone setting up a whole string of the latter from a number of phones. The way it worked was if nobody answered, you put in the code for "ring me back" and later, when someone used the phone and then hung up, the exchange would first ring your phone, then when you picked up, would ring the party you had been trying to call. All very clever, but when you set up a whole lot of these between a whole lot of phones it becomes a bit of a minefield. You just have to be careful when setting up that you don't pick up any phone that you have already set one up to, but you can set up a whole lot of them. Anyway, having committed this act of sabotage I went off to lunch myself. Luckily the boss was not the first back! The guy who was would have had no problems until either he made a call from one of the phones, or someone from outside called in. After that call was finished an he hung up, a number of phones would have started ringing. Being diligent, he would have rushed over to answer the phone, only to have another phone start to ring…Anyway, he told me that if I ever did that again he would personally kill me.
John